A PCR method is a method capable of amplifying DNA or the like hundreds of thousands times by continuously performing amplification cycles each consisting of thermal denaturation, annealing with primer, and polymerase extension reaction.
A real-time PCR method is a method capable of monitoring a PCR amplified product in real time by using a fluorescent material to detect a fluorescent signal in real time by irradiating a sample with exciting light during the progress of an amplification reaction. For example, an intercalator method is a versatile and simple method using a fluorochrome such as SYBR (Registered Trade Mark) GREEN I or the like that specifically binds to double-stranded DNA.
The real-time PCR method is useful especially for analysis of trace amounts of DNA. The real-time PCR method and therefore can be used as a detection means in medical practice or researches on gene analysis to perforin monitoring of genomic DNA, including monitoring of chemical reactions.
The real-time PCR method can use a dedicated equipment or the like that is an integrated combination of a thermal cycler capable of continuously changing the temperature of a reaction liquid and a spectrofluorophotometer in order to monitor a PCR amplified product in real time. JP-A-2003-298068 (Patent Document 1) and JP-A-2004-025426 (Patent Document 2) disclose techniques relating to temperature control during amplification reaction.
The real-time PCR method allows genetic detection to be performed in a closed system, and therefore can reduce the risk of cross contamination and is excellent in quantitative performance. However, the thermal cycler used in this method is based on the principle that the temperature of a reaction liquid for PCR contained in a tube is controlled by controlling the temperature of a metal block made of aluminum or the like in which the tube containing the reaction liquid for PCR is inserted. For this reason, it is difficult to quickly change the reaction temperature, and therefore it takes 1 hour or longer to complete the reaction.
The use of a micro-chemical reaction method disclosed in JP-A-2008-012490 (Patent Document 3) makes it possible to significantly reduce the reaction time of PCR to several minutes to more than ten minutes. According to this method, a container filled with a non-aqueous liquid such as silicone oil or the like whose specific gravity is smaller than that of water can function as a thermal cycler required for PCR by sinking a droplet composed of a reaction liquid for PCR containing magnetic particles in the non-aqueous liquid and repeatedly moving the droplet to or from a heat source or vicinity thereof with the use of a magnet provided under the container. The temperature of the reaction liquid for PCR depends on the distance from the heat source to the reaction liquid for PCR and is therefore instantaneously adjusted, which makes it possible to achieve ultrahigh-speed PCR. In addition, the droplet is controlled by magnetism applied thereto from the outside of the container and therefore cross contamination affecting the accuracy of genetic detection can be minimized, which makes it possible to achieve a perfectly-closed device for gene amplification.    Patent Document 1: JP-A-2003-2980068    Patent Document 2: JP-A-2004-025426    Patent Document 3: JP-A-2008-12490